In “Milk Like Sugar,” there are characters who are kids and characters who are parents. And then there are those who seem destined to be one and the same.

Kirsten Greenidge’s play, whose world premiere is now in previews at La Jolla Playhouse, centers on three teenage girls who make a pact to become pregnant together.

It’s not necessarily a maternal instinct that drives them, though. It’s more, says the playwright, a yearning — mixed-up and misguided, maybe, but deep nonetheless — for something to claim as their own, when everything they’re told they need can seem so out of reach.

“It’s almost like a post-traumatic stress reaction to the world,” says Greenidge, a Massachusetts native who’s making her Playhouse debut with the work. “I remember after 9/11, there was talk about people who really wanted to get married and have babies. Their world had been shaken so much that they wanted something to hold onto.

“I think that for these girls, if they could articulate it — which they can’t — that’s the tenor of this pact of wanting to be mothers.”

The idea behind the play, a co-commission of the Playhouse and Theater Masters of Aspen, Colo., crystallized for Greenidge in 2008 when she read of a pregnancy pact among a group of girls in Gloucester, Mass., not far from where she lives and teaches.

But while teen pregnancy is obviously an enduring social concern, “Milk Like Sugar” ultimately isn’t about that issue.

“The pregnancy pact is a vehicle,” she says. “But it’s really about finding your own voice in this cacophonous din of texting, and of all these images that kids get of what your life is supposed to be (as a teen). And yet that’s not the moral fiber that’s going to take you through your life in a meaningful way.

“What you put on your baby registry is not emblematic of who you are as a person. What you covet in a material way shouldn’t be who you are as a person.”

“Milk Like Sugar” is a play in which “race and class and culture all come together in a cataclysmic type of meet-and-greet,” Greenidge adds. Helping tie it all together is director Rebecca Taichman, who has had a singular summer at the Playhouse. That’s because she also directed the Playhouse’s last show — the fable-based musical “Sleeping Beauty Wakes,” which closed just a week ago.

Taichman admits with a laugh that the experience has been “like whiplash — tonally (the shows are) completely opposite experiences. (But) I think that’s one of my favorite things about directing. It’s this wormhole into completely unique worlds. It’s been pretty thrilling, actually.”

At the center of Taichman’s cast for the production is Angela Lewis as Annie, the 16-year-old who enters into the pact with two friends. The cast also includes Tony Award-winner Tonya Pinkins (“Jelly’s Last Jam,” “Caroline or Change” and the Playhouse’s “Thoroughly Modern Millie”); Cherise Boothe, an affecting presence in the off-Broadway production of the Pulitzer Prize-winning “Ruined”; plus Nikiya Mathis, LeRoy McClain, J. Mallory-McCree and Adrienne C. Moore.

To some extent, says Taichman, the play is “about seeking love. That’s one sort of big thing: the idea of a little being that’ll love you just for you, no matter what. And this is in a world where there’s not a lot of love coming at these kids from their parents and teachers,” although Taichman adds that each of the three girls’ stories is quite different.

“And there is a very strange and sad, but profoundly real feeling that if you get a baby, you’ll also get all the ‘stuff’ that comes with a baby. You’ll get a very cool stroller, you’ll get this big party.”

By contrast, it’s Annie’s birthday when the play opens, “and her mother has basically forgotten.”

Early start

Greenidge is new to the Playhouse, but not to San Diego. In 2006, Moxie Theatre premiered the playwright’s comedy “The Gibson Girl,” thanks to a connection with that theater’s founding artistic director, Delicia Turner Sonnenberg.

Greenidge’s playwriting career started at a very young age, aided by a supportive upbringing that she notes is largely at odds with the experiences of the girls in “Milk Like Sugar.”

“I had a large family that always told me, ‘You can do this. Whatever you want to do, you can do. And here are the tools that can help you do that.’ From very early on, my family was made to sit and watch my plays in the living room” — and buy tickets for the privilege.

“My family never said, ‘No, we’re not going to sit in the living room and pay to watch you.’ I mean, maybe after Hour 2, sure. But they were really very kind and generous. And now that I have my own kids, I’m realizing how generous they were!”

Greenidge now has had more than a half-dozen works produced, and also has taught widely; some of the inspiration for “Milk Like Sugar” came from stories she heard while teaching public speaking to predominantly female classes in the Boston area.

Taichman, for her part, comes from a politically engaged family in Long Island — she recalls marching around with her sister as a young girl, reciting a power-to-the-workers limerick their grandfather had taught them. Like Greenidge, she sees the search for identity as a strong thread in the story of Annie and her friends.

“I guess this idea of the struggle to find your own voice is at the heart of the play — especially in a world that’s conspiring against that individual, authentic voice. There’s a lot of information coming at you about what’s cool, how you should be. It’s sort of a bewildering process to unpack that all, and get to this kernel of authenticity within yourself.”

Yet “there’s a fierce life force” at the play’s center, Taichman adds. “There’s a lot of love. It’s not coming at you like a brutal evening of agony in the theater. It’s incredibly funny; it’s also incredibly painful.

“It is looking at painful questions, but with a really expansive tone that holds both laughter and tears.”